A popular method of displaying information is by the use of overhead transparencies. Clear plastic sheets are imprinted with information from a variety of sources, such as photocopies, desktop plotters, and hand-drawn images using ink pens. These images are then placed on an overhead protector for display. The overhead projector passes high-intensity light through the transparent images, through a set of optics, and onto a screen.
An overhead projector commonly includes a light box having a horizontal cover glass, and a lens and mirror arrangement positioned above the cover glass for projecting onto a remote viewing screen the image of a transparency positioned on the cover glass and illuminated by a light source located within the box. Usually, the changing from one transparency to the next is performed manually, with each transparency being manually placed in turn onto the light box cover glass for viewing, and then manually removed after viewing. Such procedure is not only tedious and tiresome, but makes it difficult to maintain the transparencies in proper order, particularly if some of the transparencies will be shown multiple times during the same presentation. Moreover, in order to have the correct image orientation during viewing, each transparency must be correspondingly correctly oriented on the viewing plate. This makes handling even more cumbersome, especially if the room is darkened to enhance image contrast. In the past, a variety of patents have issued relating to devices for automatically feeding a stack of transparencies, one at a time. For example, U.S. Pat. No. 5,172,145, issued on Dec. 15, 1992, to S. Stephenson describes a transparency changer arrangement in which transparencies are automatically sequentially fed by pick and retard rollers from a single enclosed cassette-loaded transparency stack. The transparencies are passed under transparent plates to belts and rollers located marginally of a viewing area of the projector. A microprocessor circuit controls the stack of transparencies so as to facilitate the selection by the user.
U.S. Pat. No. 5,059,020, issued on Oct. 22, 1991, to Jean A. Genieis teaches a device for automatically feeding a projector which includes two removable mostly enclosed cassettes, one located directly above the other. Each of these cassettes is fitted with levers carried by shafts actuated by electromagnets. Two transverse shafts above the leading edge of each cassette carry return pulleys over which belts pass for driving the top document from a stack of documents in the cassette.
U.S. Pat. No. 4,942,411, issued on Jul. 17, 1990, to S. A. Polston provides an automatic overlay feed apparatus for an overhead projector. This device includes a scrolling means including a first winding shaft and a second winding shaft for moving an overlay scroll. A plurality of sequentially arranged projectable overlay sheets are moved across the area of the projector. A motor is provided so as to rotate at least one of the winding shafts. A remote controller provides controlled operation of the motor from a remote location.
U.S. Pat. No. 4,707,092, issued on Nov. 17, 1987, to M. I. Mindell provides a transparency transport system that includes a transfer belt made of a base web and a pocket web, fused together to form a series of encapsulating pockets, for the purpose of receiving a sequence of transparencies. A platen is positioned so that the transfer belt can advance across the platen from a fan-fold supply stack next to the projector.
U.S. Pat. No. 4,368,964, issued on Jul. 18, 1983, to U. R. Carlson describes a slide projector with an automatic slide changer. Magazines are provided on each side of the optical pathway of the projector so as to support slides therein. A slide frame transport device is provided which consists of two toothed belts provided with external dog members for transporting the slide frames from one slide magazine to the other.
U.S. Pat. No. 3,594,082, issued on Jul. 20, 1971, to T. M. Lonchar teaches a slide changer attachment which includes mating case sections pivotally connected by slidable adjustable arms to the side of an overhead protector. An intermediate panel is mounted on one of the case sections and supports a sliding feed plate adjacent the bottom of the hopper. The feed plate is connected to an endless belt driven by a reversible motor controlled by a circuit including a manually actuated switch, a set of limit switches, and a relay to effect automatic reciprocation of the feed plate.
U.S. Pat. No. 4,756,616, issued on Jul. 12, 1988, to Min et al. describes an image projection system which includes a frame, a source of illumination, a projection lens, a stage mounted to the frame for projecting a transparency thereon for view, and a delivery means for gripping and slidingly moving an unframed transparency along the surface of the stage. A magazine holds a stack of unframed transparencies for insertion into the frame adjacent to the stage. A feed system is provided so as to allow for the movement of transparencies from one of the magazines to the other.
It is an object of the present invention to provide a transparency display system that allows transparencies to be displayed while allowing free movement by the displayer.
It is another object of the present invention to provide a transparency display system that can handle framed or unframed transparencies.
It is another object of the present invention to provide a transparency display system that is adaptable to a wide range of transparencies.
It is a further object of the present invention to provide a transparency display system that improves the time and effectiveness of transparency display, provides greater flexibility for the user of the system, and is very easy to operate.
It is another object of the present invention to provide a system which has open access to transparencies at every point in the system.
It is yet a further object of the present invention to provide a system that can use framed or unframed transparencies and is capable of transferring transparencies in both the portrait and landscape positions.
These and other objects and advantages of the present invention will become apparent from a reading of the attached specification and appended claims.